OBJECTIVES: The overall objectives of this research are (1) to study the biology of the mycoplasmatales with reference to elucidating the pathogenetic mechanisms of mycoplasmal diseases, particularly experimental arthritis, and (2) to relate these studies to the etiology and mechanisms of pathogenesis of human rheumatoid arthritis. GOALS FOR CURRENT YEAR: a. To find evidence for an association of mycoplasmas with human rheumatoid arthritis. b. To compare the cell-mediated immune responses of mice to infection by M. arthritidis and M. pulmonis and to elucidate the pathogenetic mechanisms of these arthritic diseases. c. To determine the arthritogenic potential of mycoplasmas in rabbits. d. To determine the role played by immunosuppression, cytotoxicity and mitogenesis in mycoplasma-induced disease. BIBLIOGRAPHIC REFERENCES: Cole, B.C., M.B. Taylor and J.R. Ward, 1975. Studies on the infectious etiology of human rheumatoid arthritis. Arth. Rheum. 18:435-441. Cole, B.C., L. Golightly-Rowland and J.R. Ward, 1975. Chronic Proliferative arthritis of mice induced by Mycoplasma arthritidis: Demonstration of a cell-mediated immune response to mycoplasma antigens in vitro. Infect. Immun. 11.1159-1161.